A positioning error in each positioning scheme will be described first.
In an independent positioning scheme in which a positioning device independently determines a position by using code information of a GNSS (Global Navigation System) signal from a satellite positioning system (GNSS) such as a GPS (Global Positioning System), a positioning accuracy is on the order of meters due to an error included in the GNSS signal.
In comparison with the independent positioning scheme using the code information, a positioning scheme using carrier-level correction data realizes highly accurate positioning on the order of centimeters.
In particular, a scheme is called a network type RTK (Realtime Kinematic) scheme in which a GNSS signal is received at a plurality of electronic reference points (distributed at intervals of ten or so kilometers in Japan), the accurate positions of which are already known, to estimate an amount of error included in the GNSS signal invertedly from the known positions of the permanent GPS stations, distribute it to a user as correction data, and perforin positioning on the order of centimeters together with a GNSS signal obtained by a positioning device on the user's side.
Such positioning scheme includes a positioning reinforcement system called a FKP (Flaechen Korrekktur Punkt) scheme.
The positioning device realizes highly accurate positioning on the order of centimeters by acquiring the correction data valid in a local area around the electronic reference point closest to the device in one-to-one communication via a communication network using terrestrial waves with abundant communication capacity such as a wireless LAN (Local Area Network) or a mobile phone, and eliminating an error included in a GPS signal with the use of the correction data.
On the other hand, the highly accurate positioning on the order of centimeters is also realized in a positioning scheme that uses an artificial satellite such as a quasi-zenith satellite to distribute correction data valid in a wide area nationwide.
In this positioning scheme, the correction data is distributed from the quasi-zenith satellite to allow a positioning device to acquire the correction data even in an environment where communication via the wireless LAN or mobile phone is not available, so that the error in the GNSS signal is eliminated by using the correction data to be able to realize the highly accurate positioning on the order of centimeters.
Patent Literature 1 discloses a scheme as the positioning scheme using the quasi-zenith satellite, for example.